Un hombre cruza distraído la calle cuando lo sorprende el bocinazo de un auto muy próximo a él. El hombre reacciona y sube a la vereda de un salto, algo agitado y tembloroso. Además de los cambios corporales citados, ¿Cuál/les otro/s pudieron haberle ocurrido ante esta situación? ¿Por qué el cuerpo responde de esa manera? ¿Cuál es la función de esos cambios?

- Dilation of the pupils

- Increased heart rate (chronotropism) and the force of contraction of the heart  (inotropism), as well as blood pressure.

- Bronchodilation to facilitate the entry of air

- Vasoconstriction in organs that are not needed, such as the abdominal viscera and the kidney

-Vasodilation of muscles, heart, liver and fat tissue

- Hepatic glycogenolysis and lipolysis of adipose tissue

- Increase in blood glucose

Physical stressors; for example cold, hypoglycemia, hemorrhage, hypoxia, necrosis, burn, acute pain are  stimuli that alter the physiological state affecting homeostatic mechanisms, and initiate an adaptive response necessary for survival. For their part, psychological stressors are stimuli that threaten the  current state of the individual or provoke a state of anticipation even though they do not pose an immediate threat  to physiological conditions; need to be processed by the cerebral cortex before initiating the stress response and  they depend largely on previous experiences.

Depending on the type of physical or psychological stress, neurons in the brain stem or those in the areas of the brain are activated.  limbic system respectively, which through axonal projections affect neurons of the nucleus  paraventricular cells of the hypothalamus that synthesize CRH (corticotropin-releasing hormone). Neurons  hypophysiotropic in response to a stimulus, releases CRH to the hypothalamic-pituitary portal circulation that reaches the  adenohypophysis and controls the synthesis and release of adrenocorticotropin (ACTH) that travels through the bloodstream  exerting its feedback mechanism on the adrenal gland. Therefore, the glucocorticoids secreted by the  adrenal gland will exert their actions on peripheral tissues as part of the adaptive response to  stress.

But in addition, the hypothalamus will be in charge of decoding neuronal signals originating in other brain sites and  hormonal signals coming from the periphery. Therefore, hypothalamic neurons not only secrete their  product towards the hypothalamic-pituitary portal blood, but also have nerve projections towards other  brain regions or to nuclei located in the spinal cord (such as the nucleus of the solitary tract) and  controlling the functioning of the autonomic nervous system. Thus the coordinated response to stress includes  adrenaline secretion from the adrenal medulla in response to stimulation of the autonomic system; this hormone  it causes a state of excitement or alertness in the body allowing it to respond to the challenge.

So, the combined action of the hormones cortisol and adrenaline and the autonomic nervous system (system  sympathetic-adrenal) allows a series of vegetative activities involving various apparatus (cardiovascular,  digestive, respiratory, muscular, etc.) and the activation of various metabolic pathways (of carbohydrates and lipids  fundamentally) to provide the immediate energy demands required before the aggressor stimulus or  stress.

Explanation:

During physical exertion or emotional stress, the Sympathetic Nervous System predominates over the Parasympathetic Nervous System. The sympathetic tone favors : intense physical activity for the production of energy in a rapid and prolonged way. The fear, the confusion, the  anger also stimulate the SNS.

The flight or fight reaction is the activation of the SNS on the adrenal medulla produces the release of adrenaline and norepinephrine, which in turn produce the following effects:

- Dilation of the pupils

- Increased heart rate (chronotropism) and the force of contraction of the heart  (inotropism), as well as blood pressure.

- Bronchodilation to facilitate the entry of air

- Vasoconstriction in organs that are not needed, such as the abdominal viscera and the kidney

-Vasodilation of muscles, heart, liver and fat tissue

- Hepatic glycogenolysis and lipolysis of adipose tissue

- Increase in blood glucose

This ensures a self-defense response when perceiving danger, activating a survival instinct